If you're already researching something, then discover the -20% research cost artifact, and then cancel the research, you are only refunded the 'new' cost, not what you actually paid for it.
Ex.
You pay 900 credits to start researching.
You discover the artifact. The price is now 720 credits.
You cancel the research and are only refunded 720 credits.
P.S thanks for a wonderful game, loving it!